According to a first concept of the invention, the invention relates to a method for transporting flat products, in particular folded products which are transferred at the end of a transport path to an assembly which forwards them and is preferably moved transversely with respect to the transport path.
A further concept of the invention relates to an apparatus which is suitable for carrying out this method, having a transport gap which is formed by conveying elements which are moved in the transport direction and lie opposite one another, it being possible to supply the products to the transport gap which is delimited on at least one side by at least one stationary guide element in the region of its end which is assigned to an assembly which forwards the products and is preferably moved transversely with respect thereto, the transport gap being assigned air nozzles which can act on the products coming out of the transport gap.
During the transport of folded products, etc., by means of a belt guidance means, there is the risk that the products are charged electrically on account of unavoidable friction. The consequence of this is that the movement of the products is impeded during the transfer to an assembly which is arranged after the belt guidance means, such as a paddle wheel, etc. This is true, in particular, at relatively low production speeds, such as occur, for example, during the starting-up operation or braking operation, where the kinetic energy of the products is not sufficiently great to overcome the tendency of the products to adhere, which is brought about on account of the electric charging. The invention is shown that, in such a case, the products can remain attached to stationary guide elements with their rear end region or to the associated paddle of the paddle wheel with their front end region. In both cases, the products do not pass entirely into the associated compartment of the paddle wheel, with the result that the rear ends can block the entrance to the next compartment, which leads to disruptions.
German Patent Document No. DE 102 19 540 B3 has disclosed an apparatus of the abovementioned type, in which blower nozzles are attached on both sides of the transport gap, which blower nozzles are directed towards the adjacent product surface and are intended to keep the latter away from stationary guide tongues. Although this counteracts the rear product ends getting caught on the stationary guide tongues, the risk of it being possible for the front end regions of the products to get caught on the associated paddle of the paddle wheel cannot be prevented with this known arrangement. It is not possible to use the known arrangement to accelerate the products in order to increase their kinetic energy to such an extent that an inclination to adhere is overcome. The same is true conversely for a braking operation.
In addition, the air jets which impact on the product surface approximately perpendicularly with respect to the latter cannot guide the products. It can therefore occur that the products become tilted, etc., which can likewise lead to disturbances.
Proceeding from this, it is the object of the present invention to improve a method and an apparatus in such a way that a high level of freedom from faults is attained.
In conjunction with the method according to the generic type, this object is achieved by the fact that, in the case of lower transport speeds, the products are accelerated during the transfer by air which passes along them at a higher speed in the transport direction than the transport speed.
The solution, in apparatus terms, of the object according to the invention consists in the fact that, in the apparatus of the generic type, the air nozzles have a jet direction which is substantially parallel to the transport plane and points in the transport direction, it being possible to apply compressed air to the air nozzles, at least in the case of lower transport speeds, in such a way that the air which emerges from them has a higher speed than the transport speed.
These measures lead to an air film which passes along the products at high speed and not only separates the products from an adjacent stationary guide element but accelerates them at the same time in the transport direction. The products are therefore not only guided reliably but are also given sufficient kinetic energy that, even in the case of an absent or weak air film, an inclination to adhere on account of electrostatic attraction is overcome. The front edges of the products therefore advantageously pass reliably as far as the base of the paddle wheel, as a result of which disturbances of the type mentioned in the introduction are avoided reliably.
Advantageous refinements and expedient developments of the superior measures are further specified. In the case of higher transport speeds, the products can thus be braked during the transfer by reducing the pressure in the gap between one of their surfaces and an adjacent guide surface. For this purpose, the air nozzles can be connected to a vacuum source, with the result that there is a drop in pressure. As a consequence of the drop in pressure, the products are attracted by suction and braked as a result. In this case, there is no need to fear that the products will get caught on account of electrostatic attraction, as the kinetic energy of the products is sufficiently high here to overcome electrostatic attraction forces.
A further expedient measure can consist in the fact that the air nozzles are assigned to a guide plate which extends over the width of the transport gap. This makes it possible to form an air film reliably over the entire width.
The guide plate can advantageously be provided with tongues which engage into grooves of an adjacent belt deflection roller. As a result, a transfer is attained which is free from disturbances.
A further, particularly expedient measure can consist in the fact that a plurality of nozzle rows which extend in the transport direction are provided over the width of the guide plate. The nozzle rows can be switched on and off individually, which makes simple adaptation to the respectively processed product format possible.